MAX3229EEBV MAXIM [Maxim Integrated Products], MAX3229EEBV Datasheet - Page 7

• Manufacturer Part Number: MAX3229EEBV
• Manufacturer: MAXIM [Maxim Integrated Products]

Figure 2a. MAX322_E Entering 1µA Supply Mode via
AutoShutdown
MAX3228E/MAX3229E maintain the outputs in regula-
tion until the battery voltage drops below +3.1V. Then
the output regulation points change to ±4.0V
When V
output voltage of ±4.0V, while V
and +3.5V. When V
age of +3.5V, the charge pump switches modes to
generate an output of ±5.5V.
Table 1 shows different supply schemes and their
operating voltage ranges.
The transmitters are inverting level translators that con-
vert CMOS-logic levels to RS-232 levels. The
MAX3228E/MAX3229E will automatically reduce the
RS-232 compliant levels (±5.5V) to RS-232 compatible
levels (±4.0V) when V
+3.1V. The reduced levels also reduce supply current
requirements, extending battery life. Built-in hysteresis
of approximately 400mV for V
232 output levels do not change if V
sudden current draw causing the supply voltage to
drop slightly. The outputs will return to RS-232 compli-
ant levels (±5.5V) when V
+3.5V.
The MAX3228E/MAX3229E transmitters guarantee a
250kbps data rate with worst-case loads of 3kΩ in par-
allel with 1000pF.
When FORCEOFF is driven to ground, the transmitters
and receivers are disabled and the outputs become
high impedance. When the AutoShutdown circuitry
senses that all receiver and transmitter inputs are inac-
tive for more than 30µs, the transmitters are disabled
and the outputs go to a high-impedance state. When
the power is off, the MAX3228E/MAX3229E permit the
transmitter outputs to be driven up to ±12V.
+0.3V
-0.3V
R_IN
*TRANSMITTERS ARE DISABLED, REDUCING SUPPLY CURRENT TO 1µA IF
ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR AT LEAST 30µs.
CC
is rising, the charge pump will generate an
_______________________________________________________________________________________
CC
rises above the switchover volt-
CC
CC
±15kV ESD-Protected +2.5V to +5.5V
falls below approximately
RS-232 Transmitters
rises above approximately
CC
CC
ensures that the RS-
COUNTER
CC
30µs
is between +2.5V
R
is noisy or has a
AND TRANSMITTERS
POWER SUPPLY
INVALID
RS-232 Transceivers in UCSP
TO MAX322 _E
The transmitter inputs do not have pullup resistors.
Connect unused inputs to GND or V
The MAX3228E/MAX3229E receivers convert RS-232
signals to logic output levels. All receivers have invert-
ing three-state outputs and can be active or inactive. In
shutdown (FORCEOFF = low) or in AutoShutdown, the
MAX3228E/MAX3229E receivers are in a high-imped-
ance state (Table 3).
The MAX3228E/MAX3229E feature an INVALID output
that is enabled low when no valid RS-232 signal levels
have been detected on any receiver inputs. INVALID is
functional in any mode (Figures 2 and 3).
Figure 2b. MAX322_E with Transmitters Enabled Using
AutoShutdown
Figure 2c. MAX322_E AutoShutdown Logic
+2.7V
-2.7V
R_IN
*TRANSMITTERS ARE ENABLED IF:
ANY RECEIVER INPUT IS GREATER THAN +2.7V OR LESS THAN -2.7V.
ANY RECEIVER INPUT HAS BEEN BETWEEN +0.3V AND -0.3V FOR LESS THAN 30µs.
V
INVALID IS AN INTERNALLY GENERATED SIGNAL
THAT IS USED BY THE AUTOSHUTDOWN LOGIC
AND APPEARS AS AN OUTPUT OF THE DEVICE.
POWER DOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
CC
V
L
FORCEOFF
FORCEON
INVALID
V
L
RS-232 Receivers
COUNTER
L
30µs
.
R
POWER DOWN
POWER SUPPLY
INVALID
TO MAX322 _E
7